I've got one. At first it seemed to do what I wanted it to... . which was to get rid of the oil leaking and smell from crankcase breather tube... . but I do notice some oil on the turbo blades when I take off the intake tubes. Now I have to admit that I am also running a filter made by K&N (which came with the Banks kit that I have on) so I cannot say for certain that the oil is coming from the AirSep.
Pros:
1) No more smell after changing oil!
2) No more oil drippings!
3) No more mess inside the engine compartment (for the most part)
4) Crankcase vacuume created to increase efficiency and engine life.
Cons:
1) Oil on turbo blades (can't say for sure its from the Airsep, though)
2) More of a PITA when changing the oil - harder to remove to get to filter.
3) Can't run the Huge air filter lots of guys are running (without some mods)
4) Expensive and not as easy to install as I thought - although I did have excellent customer service from Walker.
5) I see some oil leaking from the new oil filler cap they give you.
I must also note that I have not called Walker to ask about the oil on the turbo blades nor the leaking of the filler cap - so they haven't had the opportunity to address these issues with me.